Aromatic polycarbonate, production method and molded products thereof

ABSTRACT

An aromatic polycarbonate which has high durability and is excellent in color tone, transparency and mechanical strength, especially an aromatic polycarbonate which has high durability and stability when it is used under high temperature and high humidity conditions for a long time, and production method and use thereof. In the aromatic polycarbonate which has a sodium element content of 100 ppb or less and a content of each of Ni, Pb, Cr, Mn and Fe of 70 ppb or less and the method of producing a polycarbonate by polycondensing an aromatic dihydroxy compound and a carbonic acid diester, the above aromatic polycarbonate is produced by controlling 1) the content of sodium element contained in each of the above raw materials to 52 ppb or less, 2) the content of each of Fe, Cr, Mn, Ni and Pb to 40 ppb or less and 3) the amount of a specific catalyst to a specific value based on the content of Fe contained in the raw materials.

FIELD OF THE INVENTION

The present invention relates to an aromatic polycarbonate which has asmall content of a specific metal element and high durability andstability particularly when it is used at a high temperature and a highhumidity for a long time, production method and molded products thereof.

DESCRIPTION OF THE PRIOR ART

Aromatic polycarbonates are excellent engineering plastics which areexcellent in color, transparency and mechanical strength. Since theyhave recently been used for various purposes and under widerenvironmental conditions, high durability and stability are required ofthe polycarbonates to retain the above characteristic properties evenwhen they are used under high-temperature and high-humidity conditionsfor a long time.

It is reported that conventional aromatic polycarbonates have problemswith durability and stability because they experience a reduction inmolecular weight and deterioration in color and transparency when theyare used under high-temperature and high-humidity conditions for a longtime. A reduction in molecular weight lowers the mechanical strength ofa polymer and deterioration in color and transparency detracts greatlyfrom the advantages of the aromatic polycarbonates.

Since it is apprehended that deterioration by moist heat is caused bytrace amounts of impurities contained in the polymer, especially metalcompounds though the definite chemical structures of chemical speciesexistent in the polymer are unknown, studies are being made on themethod of purifying raw materials and the polymer and the effect ofreducing the contents of metals for heat resistant stability.

JP-A 5-148355 (the term “JP-A” as used herein means an “unexaminedpublished Japanese patent application”) discloses an aromaticpolycarbonate having an iron content of 5 ppm or less and a sodiumcontent of 1 ppm or less and JP-A 6-32885 discloses a polycarbonatehaving a total content of iron, chromium and molybdenum of 10 ppm orless and a total content of nickel and copper of 50 ppm or less.

JP-A 2-175722 teaches that a polycarbonate having an improved color toneis obtained by reducing the total content of hydrolyzable chlorine thecontent of sodium ions and iron ions in raw materials.

JP-A 11-310630 discloses a method of producing an aromatic polycarbonateby reducing impurities contained in bisphenol A as a raw material, suchas iron to 10 ppb by weight and chroman-based impurities to 40 ppm byweight. In the method, some results are achieved by improving colortone, heat resistant stability and gel.

In any one of the above cases, the contents of metals disclosed inexamples in which the optimal conditions are realized are still high inthe order of ppm and unsatisfactory to retain the excellent color,transparency and mechanical strength of an aromatic polycarbonate for along time under a severe moist heat condition disclosed by the presentinvention.

Metal species to be reduced as impurities are limited to sodium, ironand some transition metals. Required durability and stability cannot beachieved under severe conditions simply by reducing the contents ofthese metals.

Further, it has been revealed from researches conducted by the presentinventors that the stability of a polymer is not achieved simply byreducing the amounts of impurities and that the relationship between theamount of a specific impurity contained in the raw materials and anester exchange catalyst as well as the structural characteristics of apolycarbonate molecule are important factors. Attempts have been made toreduce the number of terminal phenolic hydroxyl groups in the moleculeof a polycarbonate and not more than that is made.

Problems to be Solved by of the Invention

It is an object of the present invention to provide an aromaticpolycarbonate which has excellent durability and stability and canretain its excellent color, transparency and mechanical strength for along time under a moist heat condition which cannot be conceived in theprior art.

It is another object of the present invention to provide an industriallyadvantageous method of producing the above aromatic polycarbonate of thepresent invention.

It is still another object of the present invention to provide a moldedproduct, for example, injection molded product of the above aromaticpolycarbonate of the present invention.

Other objects and advantages of the present invention will becomeapparent from the following description.

Means for Solving the Problems

Firstly, according to the present invention, the above objects andadvantages of the present invention are attained by an aromaticpolycarbonate which comprises a main recurring unit represented by thefollowing formula (1):

wherein R₁ and R₂ are each independently a hydrogen atom, alkyl grouphaving 1 to 20 carbon atoms, alkoxy group having 1 to 20 carbon atoms,cycloalkyl group having 6 to 20 carbon atoms, aryl group having 6 to 20carbon atoms, cycloalkoxy group having 6 to 20 carbon atoms or aryloxygroup having 6 to 20 carbon atoms, m and n are each independently aninteger of 0 to 4, and X is a single bond, oxygen atom, carbonyl group,alkylene group having 1 to 20 carbon atoms, alkylidene group having 2 to20 carbon atoms, cycloalkylene group having 6 to 20 carbon atoms,cycloalkylidene group having 6 to 20 carbon atoms, arylene group having6 to 20 carbon atoms or alkylene-arylene-alkylene group having 6 to 20carbon atoms, and terminal groups consisting essentially of aryloxygroups (A) and phenolic hydroxyl groups (B), the (A)/(B) molar ratiobeing 95/5 to 40/60, and which has a melt viscosity stability of 0.5% orless, a sodium metal element content of 100 ppb or less and a content ofeach of first elements, Ni, Pb, Cr, Mn and Fe of 70 ppb or less.

Secondly, according to the present invention, the above objects andadvantages of the present invention are attained by molded products ofthe aromatic polycarbonate of the present invention.

Thirdly, the above objects and advantages for the present invention areattained by a method for producing a polycarbonate which comprisespolycondensing an aromatic dihydroxy compound and a carbonic aciddiester in the presence of a catalyst containing a) at least one basiccompound selected from the group consisting of a nitrogen-containingbasic compound and a phosphorus-containing basic compound in an amountof 10 to 1,000μ chemical equivalents based on 1 mol of the aromaticdihydroxy compound and b) at least one compound selected from the groupconsisting of an alkali metal compound and an alkali earth metalcompound in an amount of 0.05 to 5μ chemical equivalents based on 1 molof the aromatic dihydroxy compound, wherein

the aromatic dihydroxy compound and the carbonic acid diester having 1)a sodium metal element content of 52 ppb or less and 2) a content ofeach of first elements Fe, Cr, Mn, Ni and Pb of 40 ppb or less are used,and 3) the amount of the basic compound based on 1 mol of the aromaticdihydroxy compound is not more than 20×(Fe*)+200 based on the totalweight Fe* (ppb) of Fe contained in the aromatic dihydroxy compound andFe contained in the carbonic acid diester.

THE PREFERRED EMBODIMENT OF THE INVENTION

The present invention will be described in detail hereinafter.

The aromatic polycarbonate of the present invention comprises the mainrecurring unit represented by the following formula (1):

wherein R₁ and R₂ are each independently an alkyl group having 1 to 20carbon atoms, alkoxy group having 1 to 20 carbon atoms, cycloalkyl grouphaving 6 to 20 carbon atoms, aryl group having 6 to 20 carbon atoms,cycloalkoxy group having 6 to 20 carbon atoms or aryloxy group having 6to 20 carbon atoms, m and n are each independently an integer of 0 to 4,and X is a single bond, oxygen atom, carbonyl group, alkylene grouphaving 1 to 20 carbon atoms, alkylidene group having 2 to 20 carbonatoms, cycloalkylene group having 6 to 20 carbon atoms, cycloalkylidenegroup having 6 to 20 carbon atoms, arylene group having 6 to 20 carbonatoms or alkylene-arylene-alkylene group having 6 to 20 carbon atoms,and terminals groups consisting essentially of aryloxy groups (A) andphenolic hydroxyl groups (B), the (A)/(B) molar ratio being 95/5 to40/60, and has a melt viscosity stability of 0.5% or less.

According to the present invention, there is provided an aromaticpolycarbonate which has excellent durability, stability and transparencywhen it is used under a severe moist heat condition which cannot beconceived in the prior art for a long time by classifying specificelements contained in the aromatic polycarbonate into some groupsaccording to the sizes of their influences and limiting the contents ofthese groups to specific values or less.

In the present invention, trace elements which are contained asimpurities in the aromatic polycarbonate and raw materials thereof areclassified into sodium and the following first to fourth groupsaccording to the sizes of their influences upon the durability, colortone and transparency of the obtained aromatic polycarbonate.

Elements of each group are as follows.

first elements: Ni, Pb, Cr, Mn and Fe

second elements: Cu, Zn, Pd, In, Si and Al

third element: Ti

fourth elements: P, N, S, Cl and Br

The aromatic polycarbonate of the present invention has a sodium metalelement content of 100 ppb or less and a content of each of the firstelements of 70 ppb or less in order to achieve excellent durability andstability when it is used under severe high-temperature andhigh-humidity conditions for a long time.

To achieve more excellent durability and stability, the aromaticpolycarbonate has a sodium metal element content of preferably 70 ppb orless, more preferably 20 ppb or less and a content of each of the firstelements of preferably 40 ppb or less, more preferably 20 ppb or less,particularly preferably 10 ppb or less.

The terminal groups of the aromatic polycarbonate of the presentinvention consist essentially of aryloxy groups (A) and phenolichydroxyl groups (B) and the (A)/(B) molar ratio is 95/5 to 40/60,preferably 90/10 to 50/50, more preferably 85/15 to 60/40, particularlypreferably 80/20 to 70/30.

In the present invention, to obtain an aromatic polycarbonate havingmore excellent durability and stability, the following relationship ispreferably established between the amount (H) (eq/ton-polycarbonate) ofthe phenolic terminal hydroxyl group and the total (Σfirst elements(ppb)) of contents of the first elements (Ni, Pb, Cr, Mn and Fe).

(H)≦ΣFirst Elements

Further, to obtain an aromatic polycarbonate having much more excellentdurability and stability, the above relationship is preferably(H)≦0.5×(Σfirst elements).

Further, to obtain an aromatic polycarbonate having further moreexcellent durability and stability, the content of each of the secondelements is preferably 20 ppb or less, the content of the third elementis preferably 1 ppb or less, and the content of each of the fourthelements is preferably 1 ppm or less.

The viscosity stability (which will be defined hereinafter) of themolten polymer of the aromatic polycarbonate of the present invention is0.5% or less. When this value is larger than 0.5%, the hydrolysisdeterioration of the aromatic polycarbonate is promoted. To ensureactual hydrolysis resistant stability, the value should be set to 0.5%or less. To this end, it is preferred that a melt viscosity stabilizerwhich will be described hereinafter should be used especially afterpolymerization to stabilize the melt viscosity of the aromaticpolycarbonate of the present invention. The melt viscosity stability isevaluated by the absolute value of a change in melt viscosity measuredat a shear rate of 1 rad/sec and 300° C. under a nitrogen stream for 30minutes and expressed as a change rate per minute.

The aromatic polycarbonate of the present invention maybe produced byany conventionally known method such as melt polymerization orinterfacial polymerization. It is preferably produced by meltpolycondensing an aromatic dihydroxy compound and a carbonic aciddiester from the viewpoints of costs including process and raw materialsand because a polymerization solvent such as chlorinated hydrocarbondoes not need to be used and an injurious compound such as phosgene doesnot need to be used as a carbonic acid ester forming compound.

The melting method is carried out by stirring an aromatic dihydroxycompound (may be abbreviated as BPA group hereinafter) and a carbonicacid diester (may be abbreviated as DPC group hereinafter) while heatingunder normal pressure and/or vacuum nitrogen atmosphere in the presenceof an ester exchange catalyst to distill off the formed alcohol orphenol derived from the carbonic acid diester. The reaction temperaturewhich changes according to the boiling point or the like of the productis generally 120 to 350° C. to remove the alcohol or phenol formed by areaction, preferably 180 to 280° C. to obtain an aromatic polycarbonatehaving a small total content of impurities, more preferably 250 to 270°C.

In the latter stage of the reaction, the system is depressurized tofacilitate the distillation off of the formed alcohol or phenol. Theinside pressure of the system in the latter stage of the reaction ispreferably 133.3 Pa (1 mmHg) or less, more preferably 66.7 Pa (0.5 mmHg)or less.

In the present invention, there is provided a method of producing anaromatic polycarbonate by melting an aromatic dihydroxy compound (BPAgroup) and a carbonic acid diester (DPC group) by heating andpolycondensing them in the presence of a catalyst containing a) at leastone basic compound (may be abbreviated as NCBA hereinafter) selectedfrom the group consisting of a nitrogen-containing basic compound and aphosphorus-containing basic compound in an amount of 10 to 1,000μchemical equivalents based on 1 mol of BPA group and b) at least onecompound (may be abbreviated as AMC hereinafter) selected from the groupconsisting of an alkali metal compound and an alkali earth metalcompound in an amount of 0.05 to 5μ chemical equivalents based on 1 molof BPA as the aromatic polycarbonate production method of the presentinvention. In the method of the present invention, BPA group and DPCgroup having an Na metal element content of preferably 52 ppb or less,more preferably 35 ppb or less, particularly preferably 6 ppb or lessand a content of each element of the first element group of preferably40 ppb or less, more preferably 23 ppb or less, particularly preferably6 ppb or less are used. The amount (μ chemical equivalents/l mol of BPAgroup) of NCBA must be not more than (20×Fe*+200) based on Fe* (totalcontent of Fe in DPC group and BPA group: ppb).

The content of each of the second elements in DPC group and BPA group ispreferably 10 ppb or less.

The content of each of the third element in DPC group and BPA group ispreferably 1 ppb or less and the content of each of the fourth elementsin DPC group and BPA group is preferably 1 ppm.

According to the present invention, an aromatic polycarbonate havingexcellent durability can be obtained by using the above BPA group andDPC group whose contents of specific elements are specific values orless as raw materials and an NCBA catalyst in a specific ratio to thecontent of iron. The contents of metals in conventionally known rawmaterials are in the order of ppm whereas the contents of metals in rawmaterials specified by the present invention are each in the order of 0to 80 ppb, specific metal elements contained in the raw materials areclassified into some groups according to the sizes of their influences,the content of each group of the specific elements is limited to aspecific value or less, the content of a specific non-metal element isspecified, and further an NCBA catalyst is used in a specific ratio tothe content of iron in the raw materials, thereby making it possible toproduce an aromatic polycarbonate having excellent durability, stabilityand transparency when it is used under a moist heat condition whichcannot be conceived in the prior art for a long time.

It is a surprising fact that impact resistance is improved by using aspecific amount of the NCBA catalyst based on an iron impurity at thetime of a heat resistance test.

When bisphenol A (may be abbreviated as BPA hereinafter) is used as BPAgroup used as a raw material in the present invention, an aromaticpolycarbonate which is more excellent in color tone can be produced byspecifying the total content of organic impurities. That is, BPA havinga ratio of the total of the absorption peak areas of a group ofcompounds (to be referred to as “compound group A” hereinafter) elutingfor 15.5 to 24 minutes to the absorption peak area of BPA of 2.0×10⁻³ orless, preferably 1.0×10⁻³ or less when it is measured by specifichigh-speed liquid chromatography (using a 0.1% phosphoric acid aqueoussolution as an elute A and acetonitrile as an elute B, this measurementis carried out at a total flow rate of the elute A and the elute B of0.9 ml/min when the elute A/elute B ratio is 1:1 for 5 minutes after thestart of measurement with a high-speed liquid chromatograph comprising acolumn having an inner diameter of 4.6 mm and a length of 250 mm, filledwith an adsorbent (Inertosil ODS-3 adsorbent of GL Science Co., Ltd.)prepared by bonding 15% (amount of carbon) of an octadecyl group to ahigh-purity spherical silica gel having a pore diameter of 100 Å andmaintained at 40° C.±0.1° C., and then gradient operation is carried outby continuously increasing the amount of the elute B after 5 minutesfrom the start of measurement so that the elute A/the elute B becomes0:1 in 55 minutes after the start of measurement while the total flowrate is fixed, to analyze BPA with a detector for ultraviolet lighthaving a wavelength of 254 nm) is used.

More preferably, BPA having a ratio of the total of the absorption peakareas of a group of compounds (to be referred to as “compound group B”hereinafter) eluting for 22 to 24 minutes to the absorption peak area ofBPA of 5×10⁻⁵ (50 ppm) or less, preferably a ratio of the total of theabsorption peak areas of compounds having a molecular weight of 307 to309 eluting for 22 to 24 minutes to the absorption peak area of BPA of2×10⁻⁵ (20 ppm) or less when it is measured by the above specifichigh-speed liquid chromatography is used.

Much more preferably, BPA having a content of 1-naphthol. represented bythe following formula (2):

wherein R₃ and R₄ are each independently methyl, ethyl, n-propyl,isopropyl or isopropenyl, of 2×10⁻⁴ part or less by weight, preferably1×10⁻⁴ part or less by weight based on 1 part by weight of BPA is used.In the above formula (2), R₃ and R₄ can be bonded to the 2- to8-position other than the 1-position (substituted by a hydroxyl group)of a naphthalene ring separately.

Further more preferably, BPA having a content of a paraflavan compoundrepresented by the following formula (3):

wherein R₅ to R₇ are each independently an alkyl group having 1 to 4carbon atoms, R₈ and R₉ are each independently an alkyl group having 1to 4 carbon atoms, and p and q are each independently an integer of 0 to4, of 5×10⁻⁵ part or less by weight based on 1 part by weight of BPA anda content of a codimer derivative represented by the following formula(4):

wherein R₁₀ to R₁₂ are each independently an alkyl group having 1 to 4carbon atoms, R₁₃ and R₁₄ are each independently an alkyl group having 1to 4 carbon atoms, and s and t are each independently an integer of 0 to4, of 5×10⁻⁵ part or less by weight based on 1 part by weight of BPA isused.

Further more preferably, BPA having a content of a chromene compoundrepresented by the following formula (5):

wherein R₁₅ to R₁₇ are each independently an alkyl group having 1 to 4carbon atoms, R₁₈ is an alkyl group having 1 to 4 carbon atoms, and a isan integer of 0 to 4, of 1×10⁻⁵ part or less by weight based on 1 partby weight of BPA and a content of a xanthene represented by thefollowing formula (6):

wherein R₁₉ and R₂₀ are each independently an alkyl group having 1 to 4carbon atoms, R₂₁ and R₂₂ are each independently an alkyl group having 1to 4 carbon atoms, and b and c are each independently an integer of 0 to4, of 1×10⁻⁵ part or less by weight based on 1 part by weight of BPA isused.

Examples of the 1-naphthol represented by the above formula (2) include2,4-dimethyl-1-hydroxynaphthalene, 2,6-dimethyl-1-hydroxynaphthalene,2,7-dimethyl-1-hydroxynaphthalene, 3,6-dimethyl-1-hydroxynaphthalene,2-isopropyl-1-hydroxynaphthalene and 6-isopropenyl-1-hydroxynaphthalene.

Examples of the paraflavan compound represented by the above formula (3)include 2-(4-hydroxyphenyl)-2,4,4-trimethylchroman,2-(3-methyl-4-hydroxyphenyl)-2,4,4-trimethylchroman,2-(3,5-dimethyl-4-hydroxyphenyl)-2,4,4-trimethylchroman,2-(3,5-dimethyl-4-hydroxyphenyl)-2,4,4-trimethylchroman and2-(3-methyl-4-hydroxyphenyl)-2,4,4,8-tetramethylchroman.

Examples of the codi-mer derivative represented by the above formula (4)include 4-(4-hydroxyphenyl)-2,2,4-trimethylchroman,4-(3-methyl-4-hydroxyphenyl)-2,2,4-trimethylchroman, 4-(3,5-dimethyl-4-hydroxyphenyl) -2,2,4-trimethylchroman,4-(3,5-dimethyl-4-hydroxyphenyl)-2,2,4-trimethylchroman and4-(3-methyl-4-hydroxyphenyl)-2,4,4,8-tetramethylchroman.

Examples of the chromene compound represented by the above formula (5)include 2,2,4-trimethylchroman-(3)-ene,2,2-dimethyl-4-ethylchroman-(3)-ene,2,2-dimethyl-4-ethylchroman-(3)-ene, 2,2,6-trimethylchroman-(3)-ene,2,2-dimethyl-6-ethylchroman-(3)-ene, 2,2,4,6-tetramethylchroman-(3)-eneand 2,2,4-trimethyl-7-butylchroman-(3)-ene.

Examples of the xanthene represented by the above formula (6) include9,9-dimethylxanthene, 2-butyl-9,9-dimethylxanthene,3-methyl-9,9-diethylxanthene, 9,9-diethylxanthene, 9-methylxanthene and2,6,9,9-tetramethylxanthene.

Bisphenol A is produced by dehydrating and condensing acetone and excessphenol in the presence of an acid catalyst such as a uniform acidexemplified by hydrochloric acid or a solid acid exemplified by an ionexchange resin. The bisphenol A obtained by the above production methodis easily acquired as a commercially available product and generallycontains compounds (impurities) represented by the above formulas (2) to(6).

A conventionally known dihydroxy compound can be advantageously used asBPA group in the present invention. Illustrative examples of thedihydroxy compound include 2,2-bis(4-hydroxyphenyl)propane (that is,BPA), abis(2-hydroxyphenyl)methane, bis(4-hydroxyphenyl)methane,1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxyphenyl)propane,2,2-bis(2-hydroxyphenyl)propane,2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane,2,2-bis(4-hydroxy-3,5-dibromophenyl)propane,2,2-bis(4-hydroxy-3-methylphenyl)propane,2,2-bis(4-hydroxyphenyl)pentane, 3,3-bis(4-hydroxyphenyl)pentane,1,1-bis(4-hydroxyphenyl)cyclohexane, bis(4-hydroxyphenyl)sulfide,bis(4-hydroxyphenyl)sulfone and compounds obtained by substituting anaromatic ring of these compounds by an alkyl group or aryl group. Out ofthese, BPA is particularly preferred from an economical point of view.They may be used alone or in combination of two or more.

Illustrative examples of the DPC group include diphenyl carbonate (maybe abbreviated as DPC hereinafter), bis(diphenyl)carbonate, dimethylcarbonate, diethyl carbonate and dibutyl carbonate. Out of these, DPC ispreferred from an economical point of view.

An aromatic polycarbonate which has low contents of specific metalelements contained as impurities as described above and is excellent indurability, color tone and transparency can be obtained by purifying BPAand DPC used as raw materials or by purifying an aromatic polycarbonate.

BPA group and DPC group used as raw materials can be purified by a knownpurification method such as distillation, extraction, recrystallizationor a combination thereof.

Besides the above methods, the raw materials are also preferablypurified by sublimation at a temperature as low as possible for a longtime, more preferably a combination of sublimation and any one of theabove purification methods.

The contents of the above impurity elements can be reduced from thelevel of ppm to the level of ppb which is 1/1,000 or less of the abovelevel by these methods. In addition, the contents of the above organicimpurities which have not had attracted much attention can be reduced topredetermined values.

The aromatic polycarbonate can be purified by such a method as the waterwashing or reprecipitation of a polymer solution. As for the waterwashing of a polymer, the polymer solution is preferably fullydehydrated after washing. As for dehydration, a treatment with a silicagel or filtration with a fine porous filter is used. The reprecipitationof a polymer is carried out by adding a poor solvent for a polymer suchas methanol or acetonitrile to a polymer solution in a solvent such asmethylene chloride or 1-methyl-2-pyrrolidinone (may be abbreviated asNMP hereinafter). In order to obtain a polymer having high purity, it ispreferred that the poor solvent be gradually added over a long time.

That is, in order to obtain an aromatic polycarbonate having smallcontents of impurity elements, it is preferred that the raw materialspurified by any one of the above methods be used to produce a polymerand the obtained polymer be further purified by any one of the abovemethods.

To obtain the aromatic polycarbonate having small contents of impurityelements of the present invention, a high-purity solvent havingextremely small contents of impurity elements is preferably used for thepurification of the raw materials and polymer. To this end, a solventfor the electronic industry may be used.

In the present invention, a specific catalyst, that is, at least onecatalyst selected from a) at least one basic compound (NCBA) selectedfrom the group consisting of a nitrogen-containing basic compound and aphosphorus-containing basic compound and b) at least one compound (AMC)selected from the group consisting of an alkali metal compound and analkali earth metal compound is preferably used for the ester exchangemelt polymerization of the aromatic polycarbonate.

Illustrative examples of the catalyst NCBA are given below. Examples ofthe nitrogen-containing basic compound include ammonium hydroxideshaving an alkyl, aryl or alkylaryl group such as tetramethylammoniumhydroxide (Me₄NOH), tetrabutylammonium hydroxide (BU₄NOH),benzyltrimethylammonium hydroxide (φ-CH₂(Me)₃NOH) andhexadecyltrimethylammonium hydroxide; basic ammonium salts having analkyl, aryl or alkylaryl group such as tetramethylammonium acetate,tetraethylammonium phenoxide, tetrabutylammonium carbonic acid salts,benzyltrimethylammonium benzoic acid salts andhexadecyltrimethylammonium ethoxide; tertiary amines such astriethylamine, dimethylbenzylamine and hexadecyldimethylamine; and basicsalts such as tetramethylammonium borohydride (Me₄NBH₄),tetrabutylammonium tetraphenyl borate (BU₄NBPh₄) and tetramethylammoniumtetraphenyl borate (Me₄NBPh₄).

Examples of the phosphorus-containing basic compound include phosphoniumhydroxides having an alkyl, aryl or alkylaryl group such astetrabutylphosphonium hydroxide (Bu₄POH), benzyltrimethylphosphoniumhydroxide (φ-CH₂(Me)₃POH) and hexadecyltrimethylphosphonium hydroxide;and basic salts such as tetrabutylphosphonium borohydride (Bu₄PBH₄),tetrabutylphosphonium tetraphenyl borate (Bu₄PBPh₄) andtetramethylphosphonium tetraphenyl borate (Me₄PBPh₄).

The above NCBA is preferably used in an amount of 10 to 1,000μ0equivalents in terms of basic nitrogen atoms or basic phosphorus atomsbased on 1 mol of BPA group. It is more preferably used in an amount of20 to 500μ chemical equivalents, particularly preferably 50 to 500μchemical equivalents based on the same standard.

It has been discovered that use of NCBA in an amount of not more than(20×Fe*+200) μ chemical equivalents based on the total weight (Fe*, ppb)of iron contained in the DPC group and BPA group raw materials isparticularly effective in improving the color of the obtained aromaticpolycarbonate. The amount is particularly preferably not more than(20×Fe*+150) μ chemical equivalents.

Although the reason for this is not made clear, it is presumed that theinteraction between iron contained in the DPC and BPA raw materials andNCBA deteriorates the color tone of the aromatic polycarbonate. In thissense, it is preferred to reduce the contents of impurity elements asmuch as possible.

Further, in the present invention, to reflect the effect of reducingimpurities contained in the raw materials upon the color tone andstability of a polymer, AMC is used in conduction with NCBA. A compoundcontaining an alkali metal compound is preferably used as AMC. Thealkali metal compound is used in an amount of 5×10⁻⁸ to 5×10⁻⁶ chemicalequivalent in terms of an alkali metal element based on 1 mol of BPAgroup. Use of the catalyst in the above molar ratio is preferred becauseit can suppress unfavorable phenomena such as a branching reaction whichreadily occurs during a polycondensation reaction, a main chain cleavagereaction, the formation of foreign matter in an apparatus at the time ofmolding and yellowing without impairing the rate of the terminal cappingreaction of each molecule and the rate of a polycondensation reaction.

Outside the above range, the alkali metal compound exerts a badinfluence upon the physical properties of the obtained aromaticpolycarbonate, an ester exchange reaction hardly proceeds to the full,and an aromatic polycarbonate having a high molecular weight is hardlyobtained disadvantageously.

The catalyst AMC is, for example, a hydroxide, bicarbonate, carbonate,acetate, nitrate, nitrite, sulfite, cyanate, thiocyanate, stearate,borohydride, benzoate, hydrogenphosphate, or bisphenol or phenol salt ofan alkali metal or alkali earth metal.

Examples of the AMC include sodium hydroxide, lithium hydroxide, sodiumbicarbonate, potassium bicarbonate, sodium carbonate, lithium carbonate,cesium carbonate, sodium acetate, lithium acetate, sodium nitrate,rubidium nitrate, sodium nitrite, rubidium nitrite, potassium sulfite,sodium cyanate, potassium cyanate, sodium thiocyanate, potassiumthiocyanate, lithium thiocyanate, cesium thiocyanate, sodium stearate,lithium stearate, cesium stearate, sodium borohydride, lithiumborohydride, sodium tetraphenyl borate, sodium benzoate, disodiumhydrogenphosphate, dipotassium hydrogenphosphate, disodium salts,dilithium salts, monosodium salts, sodium potassium salts and sodiumlithium salts of bisphenol A, and sodium salts and lithium salts ofphenol.

The alkali metal compound may be (a) the ate-complex alkali metal saltof the group XIV element of the periodic table or (b) the alkali metalsalt of the oxo acid of the group XIV element of the periodic table. Thegroup XIV element of the periodic table is silicon, germanium or tin.

By using the alkali metal compound as a polycondensation reactioncatalyst, a polycondensation reaction can proceed quickly and completelyas described above. In addition, these alkali metal compound can controlan undesired secondary reaction such as a branching reaction whichproceeds during the polycondensation reaction to a low level.

What are enumerated in JP-A 7-268091 may be used as (a) the ate-complexalkali metal salt of the group XIV element of the periodic table, asexemplified by NaGe(OMe)₅, NaGe(OPh)₅, LiGe(OPh)₅, NaSn(OMe)₃,NaSn(OMe)₅ and NaSn(OPh)₅.

(b) The alkali metal salt of the oxo acid of the group XIV element ofthe periodic table is preferably the alkali metal salt of silicic acid,stannic acid, germanic (II) acid or germanic (IV) acid.

Illustrative examples of the above alkali metal salt include disodiumorthosilicate, tetrasodium orthosilicate, disodium monostannate,monosodium germanate (II) (NaHGeO₂), disodium orthogermanate (IV) anddisodium digermanate (IV) (Na₂Ge₂O₅).

In the polycondensation reaction of the present invention, at least onecompound selected from the group consisting of oxo acids and oxides ofthe group XIV elements of the periodic table and alkoxides andphenoxides of the same elements may be optionally used as a co-catalysttogether with the above catalyst. By using the co-catalyst in a specificamount, undesired phenomena such as a branching reaction which readilyoccurs during a polycondensation reaction, a main chain cleavagereaction, the formation of foreign matter in an apparatus at the time ofmolding and yellowing without impairing the rate of a terminal cappingreaction and the rate of a polycondensation reaction can be suppressedmore effectively.

The oxo acids of the group XIV elements of the periodic table includesilicic acid, stannic acid and germanic acid.

The oxides of the group XIV elements of the periodic table includesilicon dioxide, tin dioxide, germanium dioxide, silicon tetrabutoxide,silicon tetraphenoxide, tetraethoxy tin, tetraphenoxy tin, tetramethoxygermanium, tetrabutoxy germanium, tetraphenoxy germanium and condensatesthereof.

The co-catalyst is preferably used in such a proportion that the amountof the group XIV element of the periodic table becomes 50 molar atoms orless based on 1 molar atom of an alkali metal element contained in thepolycondensation reaction catalyst. When the co-catalyst is used in sucha proportion that the amount of the metal element becomes more than 50molar atoms, the polycondensation reaction slows down disadvantageously.

The co-catalyst is more preferably used in such a proportion that theamount of the group XIV element of the periodic table becomes 0.1 to 30molar atoms based on 1 molar atom of the alkali metal element containedin the polycondensation reaction catalyst.

Since a sodium compound has a smaller influence upon the durability ofthe produced aromatic polycarbonate than alkali metal and alkali earthmetal compounds other than sodium compounds, the sodium compound ispreferably used as a catalyst to obtain an aromatic polycarbonate havingexcellent durability in the present invention.

When AMC is used as a polymerization catalyst, it is preferably used inan amount of 0.05 to 5μ chemical equivalents, more preferably 0.07 to 3μchemical equivalents, particularly preferably 0.07 to 2μ chemicalequivalents based on 1 mol of BPA group.

When a sodium compound is used as a catalyst, sodium derived from thecatalyst is added to a polymer in addition to sodium derived from rawmaterials. Therefore, it is understood that the sodium compound catalystmust be used in such an amount that the total content of a sodium metalelement contained in the polymers should not exceed a specific value inthe present invention.

In the present invention, to obtain an aromatic polycarbonate whichhardly experiences a reduction in molecular weight and coloring,attention is paid to the viscosity stability (to be defined hereinafter)of a molten polymer and the viscosity stability must be reduced to 0.5%or less. When this value is large, the hydrolysis deterioration of thearomatic polycarbonate is promoted. To secure actual hydrolysisresistant stability, this value should be reduced to 0.5% or less. Tothis end, a melt viscosity stabilizer is preferably used afterpolymerization to stabilize melt viscosity. The melt viscosity stabilityis evaluated by the absolute value of a change in melt viscositymeasured at a shear rate of 1 rad./sec and 300° C. under a nitrogenstream for 30 minutes and expressed as a change rate per minute.

The melt viscosity stabilizer in the present invention has the functionof deactivating part or all of the activity of a polymerization catalystused for the production of an aromatic polycarbonate.

The melt viscosity stabilizer may be added while a polymer is moltenafter polymerization or remolten and added after a polycarbonate ispelletized. In the former case, the melt viscosity stabilizer may beadded while a polycarbonate which is a reaction product in a reactor orextruder is molten, or may be added and kneaded while the obtainedpolycarbonate after polymerization passing through an extruder from areactor is pelletized.

Known melt viscosity stabilizers may be used. Sulfonic acid compoundssuch as organic sulfonic acid salts, organic sulfonic acid esters,organic sulfonic anhydrides and organic sulfonic acid betaines arepreferred and phosphonium salts of sulfonic acid and/or ammonium saltsof sulfonic acid are more preferred because they have the large effectof improving the physical properties such as color, heat resistance andboiling water resistance of the obtained polymer. Out of these,tetrabutylphosphonium dodecylbenzene sulfonate and tetrabutylammoniump-toluene sulfonate are particularly preferred examples.

The polymer of the present invention can be obtained by the abovemethod. A conventionally known processing stabilizer, heat resistantstabilizer, antioxidant, ultraviolet light absorber, antistatic agent,flame retardant, release agent and the like may be added according toapplication purpose to form moldings from the polymer.

A heat stabilizer may be used to prevent a reduction in the molecularweight of the aromatic polycarbonate of the present invention anddeterioration in the color of the aromatic polycarbonate of the presentinvention. Examples of the heat stabilizer include phosphorous acid,phosphoric acid, phosphonous acid, phosphonic acid and esters thereof.Bis(2,4-di-tert-butylphenyl)pentaerythrityl diphosphite,tris(2,4-di-tert-butylphenyl)phosphite, 4,4′-biphenylene diphosphinicacid tetrakis(2,4-di-tert-butylphenyl), trimethylphosphate and dimethylbenzene phosphonate are preferably used. These heat stabilizers may beused alone or in combination of two or more. The amount of the heatstabilizer is preferably 0.0001 to 1 part by weight, more preferably0.0005 to 0.5 part by weight, much more preferably 0.001 to 0.1 part byweight based on 100 parts by weight of the aromatic polycarbonate.

To further improve releasability from a metal mold at the time of meltmolding, a release agent may be mixed with the aromatic polycarbonate ofthe present invention in limits that do not impair the object of thepresent invention. Examples of the release agent include olefin-basedwax, olefin-basedwax containing a carboxyl group and/or carboxylicanhydride group, silicone oil, organopolysiloxane, higher fatty acidesters of monohydric and polyhydric alcohols, paraffin wax and beeswax.The amount of the release agent is preferably 0.01 to 5 parts by weightbased on 100 parts by weight of the aromatic polycarbonate.

Out of the higher fatty acid esters, a partial ester or whole ester of amonohydric or polyhydric alcohol having 1 to 20 carbon atoms and asaturated or unsaturated fatty acid having 10 to 30 carbon atoms ispreferred. Preferred examples of the partial ester or whole ester of amonohydric or polyhydric alcohol and a saturated or unsaturated fattyacid include glycerol monostearate, glycerol tristearate andpentaerythritol tetrastearate. The amount of the release agent ispreferably 0.01 to 5 parts by weight based on 100 parts by weight of thearomatic polycarbonate.

An inorganic or organic filler may be mixed with the aromaticpolycarbonate of the present invention in limits that do not impair theobject of the present invention to improve rigidity. Examples of theinorganic filler include lamellar or granular inorganic fillers such astalc, mica, glass flake, glass bead, calcium carbonate and titaniumoxide; fibrous fillers such as glass fiber, glass milled fiber,wollastonite, carbon fiber, aramide fiber and metal-based conductivefiber; and organic particles such as crosslinked acrylic particles andcrosslinked silicone particles. The amount of the inorganic or organicfiller is preferably 1 to 150 parts by weight, more preferably 3 to 100parts by weight based on 100 parts by weight of the aromaticpolycarbonate.

The inorganic filler usable in the present invention may be surfacetreated with a silane coupling agent or the like. A good result such asthe suppression of the decomposition of the aromatic polycarbonate isobtained by this surface treatment.

Another resin may be mixed with the aromatic polycarbonate of thepresent invention in limits that do not impair the object of the presentinvention.

Examples of the another resin include polyamide resin, polyimide resin,polyether imide resin, polyurethane resin, polyphenylene ether resin,polyphenylene sulfide resin, polysulfone resin, polyolefin resin such aspolyethylene and polypropylene, polyester resins such as polyethyleneterephthalate and polybutylene terephthalate, amorphous polyacrylateresin, polystyrene resin, acrylonitrile/styrene copolymer (AS resin),acrylonitrile/butadiene/styrene copolymer (ABS resin), polymethacrylateresin, phenolic resin and epoxy resin.

The aromatic polycarbonate of the present invention is excellent in theeffect of retaining durability, especially durability under severetemperature and humidity conditions for a long time. Therefore,substrates for high-density optical disks typified by compact disks(CD), CD-ROM, CD-R, CD-RW, magnet optical disks (MO), digital versatiledisks (DVD-ROM, DVD-Video, DVD-Audio, DVD-R, DVD-RAM, etc.) obtainedfrom this polymer can have high reliability for a long time. It isparticularly useful for high-density optical disks such as digitalversatile disks.

Sheets obtained from the aromatic polycarbonate of the present inventionare excellent in adhesion and printability. Therefore, making use oftheir characteristic properties, they are widely used in electric parts,construction parts, auto parts and the like, specifically glazing partsproducts for widow materials, that is, glazing parts window materialsfor general houses, gyms, baseball domes and vehicles (constructionmachines, automobiles, buses, Shinkansen, trains, etc.), side wallplates (wainscots for sky domes, top lights, arcades and condominiums,side walls along roads), window materials for vehicles, displays andtouch panels for OA equipment, membrane switches, photo covers,polycarbonate resin laminated boards for water tanks, front panels forprojection TVs and plasma displays, Fresnel lenses, and optical productssuch as optical cards, optical disks, liquid crystal cells produced bycombining polarization plates, and phase difference compensators. Thethickness of the aromatic polycarbonate sheet is not particularlylimited but generally 0.1 to 10 mm, preferably 0.2 to 8 mm, particularlypreferably 0.2 to 3 mm. Processing treatments (such as lamination forimproving weatherability, scuffing resistance improving treatment forimproving surface hardness, surfacing with a matt finish or embossingfinish and treatments for obtaining a translucent surface and opaquesurface) for providing new functions to the aromatic polycarbonate sheetmay be made.

The aromatic polycarbonate of the present invention is mixed with theabove additives by any means such as a tumbler, V-shaped blender, supermixer, “Nauter” mixer, Banbury mixer, kneading roll, extruder or thelike. The thus obtained aromatic polycarbonate resin composition can beformed into a sheet by melt extrusion directly or after it is pelletizedby a melt extruder.

Moldings having excellent durability and stability can be obtained fromthe aromatic polycarbonate of the present invention by molding such asinjection molding.

The aromatic polycarbonate of the present invention may be used for anypurpose. As partly described above, it can be advantageously used inelectronic and communication equipment, OA equipment, optical parts suchas lenses, prisms, optical disk substrates and optical fibers,electronic and electric materials for home electric appliances, lightingmembers and heavy electric members, car interiors and exteriors,precision machinery, machine materials such as insulating materials,medical materials, security and protection materials, sports and leisuregoods, sundry goods such as household goods, container and packingmaterials, display and ornament materials and composite materials ofother resins and organic or inorganic materials.

The aromatic polycarbonate of the present invention is particularlypreferably used in an optical disk substrate due to its excellentdurability and stability.

EXAMPLES

The following examples are provided for the purpose of furtherillustrating the present invention but are in no way to be taken aslimiting. Methods for testing aromatic polycarbonates produced in theexamples are as follows.

1) Viscosity Average Molecular Weight (Mw)

This is obtained from an intrinsic viscosity ([η]) measured in methylenechloride at 20° C. by an Ubbelohde's viscometer according to thefollowing expression.

[η]=1.23×10⁻⁴ Mw^(0.83)

2) Determination of Contents of Metal Impurities

The contents of metals contained in a polymer are determined by drawinga calibration curve for a solution of 0.5 g of the polymer dissolved in25 g of NMP for the electronic industry by the ICP-MS SPQ9000 of SeikoInstrument Co., Ltd. to be measured.

3) High-speed Liquid Chromatography of BPA Column

A column having an inner diameter of 4.6 mm and a length of 250 mm,filled with the Inertosil ODS-3 adsorbent of GL Science Co., Ltd.prepared by bonding 15% (amount of carbon) of an octadecyl group to ahigh-purity spherical silica gel having a pore diameter of 100 Å, isused and maintained at 40±0.1° C.

Eluting Conditions

Using a 0.1% phosphoric acid aqueous solution as an elute A andacetonitrile as an elute B, measurement is carried out at a total flowrate of the elute A and the elute B of 0.9 ml/min when the ratio of theelute A to the elute B is 1:1 for 5 minutes after the start ofmeasurement, and then gradient operation is carried out by continuouslyincreasing the amount of the elute B after 5 minutes from the start ofmeasurement until the ratio of the elute A to the elute B becomes 0:1 in55 minutes after the start of measurement while the total flow rate isfixed. 0.1% phosphoric acid aqueous solution: phosphoric acid of JISspecial grade or higher is diluted with distilled water for high-speedliquid chromatography to 0.1±0.0001%, elute B: acetonitrile forhigh-speed liquid chromatography is used. chromatograph: LC-10A ofShimadzu Corporation. detector; detector for ultraviolet light having awavelength of 254 nm

a) Analysis of Compound Group A

The ratio of the total of the absorption peak areas of compounds elutingfor 15.5 to 24 minutes to the absorption peak area of BPA when 2 g ofBPA is dissolved in 3 ml of acetonitrile and analyzed is measured. WhenBPA having a value of 2.0×10⁻³ or less as the above ratio is used, apolycarbonate having an excellent level of color can be produced.

b) Analysis of Compound Group B

The ratio of the total of the absorption peak areas of compounds elutingfor 22 to 24 minutes to the absorption peak area of BPA when 2 g of BPAis dissolved in 3 ml of acetonitrile and analyzed is measured. When BPAhaving a value of 50 ppm or less as the above ratio is used, apolycarbonate having an excellent level of color can be produced.

4) Melt Viscosity Stability

The melt viscosity stability of a polymer is evaluated. The absolutevalue of a change in melt viscosity is measured under a nitrogen streamat a shear rate of 1 rad./sec and 300° C. by the RAA fluidity analyzerof Rheometrics Co., Ltd. for 30 minutes to obtain a change rate perminute. When the aromatic polycarbonate has excellent stability for along time, this value does not exceed 0.5%.

5) Temperature and Humidity Deterioration Test of Aromatic Polycarbonate

To test the long-term durability under severe high-temperature andhigh-humidity conditions of an aromatic polycarbonate, the aromaticpolycarbonate is maintained at a temperature of 90° C. and a relativehumidity of 90% for 1,000 hours. 10 samples are prepared for eachpolymer and the following measurements are made to evaluate each polymerbased on mean values.

5-1) Deterioration in Color

The color of a polymer chip is measured by the Z-1001DP color differencemeter of Nippon Denshoku Co., Ltd. The larger the L value the brighterthe polymer chip becomes and the smaller the b value the less thepolymer chip yellows. When a reduction in L value and an increase in bvalue (Δb value in the table) are 1.0 or less, it is evaluated that thepolymer chip retains desired color stability even when it is used undersevere temperature and humidity conditions for a long time.

5-2) Transparency

A plate measuring 50×50×5 mm is molded by the Neomat N150/75 injectionmolding machine of Sumitomo Heavy Industries, Ltd. at a cylindertemperature of 280° C. and a molding cycle of 3.5 seconds and measuredfor its total light transmittance by the NDH-Σ180 of Nippon DenshokuCo., Ltd. The higher the total light transmittance the higher thetransparency becomes. When the plate has a total light transmittanceretention of 90% or more after a deterioration test, it is evaluatedthat the plate retains desired transparency even when it is used undersevere temperature and humidity conditions for a long time.

5-3) Moist Heat Stability of Impact Resistance

This is evaluated based on ASTM D-256 Izod impact strength (notched).After the polymer is dried at 120° C. under high vacuum for 12 hours, ametal mold is used to form a 3.2 mm thick injection molded plate. TheIzod impact strength retention of this plate before and after a moistheat treatment is obtained. When the plate has a retention of 90% ormore, it is judged that the plate retains desired strength under along-term moist heat condition.

6) Determination of Concentration of Terminal Hydroxyl Groups, and ofNumber of Aryloxy Terminals

0.02 g of a polymer sample is dissolved in 0.4 ml of heavy chloroform tomeasure the concentration of OH terminals using ¹H-NMR (EX-270 of JEOLLtd.) at 20° C. The number of aryloxy terminal groups is calculated as adifference between the total number of terminals obtained from thefollowing expression and the number of OH terminals.

total number of terminals=56.54/[η]^(1.4338)

7) Melt Hazen Color Number (APHA)

“Pyrex” color comparison tube with a flat bottom having a diameter of 23mm and a thickness of 1.5 mm is used to compare its melt hazen colornumber with that of a hazen standard color comparison liquid at a liquiddepth of 140 mm in a molten state based on a color number test methodspecified in JIS K-4101.

Measurement Method

54 g of bisphenol A and 2 mg of tetramethylammonium hydroxide arecharged, and the melt hazen color number of the resulting mixture in amolten state in the atmosphere at 175° C. and the melt hazen colornumber after the resulting mixture is maintained at 175° C. for 2 hoursare measured.

Measurement Method

54 g of diphenyl carbonate and 2 mg of tetramethylammonium hydroxide arecharged, and the melt hazen color number of the resulting mixture in amolten state in the atmosphere at 250° C. and the melt hazen colornumber after the resulting mixture is maintained at 250° C. for 2 hoursare measured.

When bisphenol A has a melt hazen color number of 20 or less at 175° C.and a melt hazen color number of 40 or less after it is maintained at175° C. for 2 hours, it can be used as a raw material for apolycarbonate.

When diphenyl carbonate has a melt hazen color number of 10 or less at250° C. and a melt hazen color number of 20 or less after it ismaintained at 250° C. for 2 hours, it can be used as a raw material fora polycarbonate.

Purification of Raw Materials

Bisphenol A (BPA) and diphenyl carbonate (DPC) purified as follows wereused as raw materials for an aromatic polycarbonate.

1) Purification of BPA

1)-1 Sublimation Purification

Commercially available BPA was charged into a glass sublimation purifierto carry out sublimation purification slowly under a nitrogen atmosphereat a pressure of 13 Pa (0.1 Torr) and a temperature of 140° C. for 5hours using a decompressor to obtain purified BPA. Sublimationpurification was repeated 2 to 4 times as required to prepare purifiedsamples.

As for the obtained purified BPA, a sample obtained by carrying outsublimation purification once was designated as Aa*1, a sample obtainedby carrying out sublimation purification twice was designated as Aa*2,and samples obtained by carrying out sublimation purification 3 times, 4times and n times were designated as Aa*3, Aa*4, . . . , Aa*n.

1)-2 Washing Purification

Sublimation purified BPA Aa*1 was rinsed with acetone or methanol anddried. The samples were designated as A-Rac and A-Rme.

1)-3 Recrystallization Purification

Commercially available BPA was recrystallized from acetone and driedunder vacuum. A sample obtained by carrying out recrystallization oncewas designated as Ab*1 and a sample obtained by carrying outrecrystallization twice was designated as Ab*2.

Separately from these, a purified bisphenol sample Aab*2 was prepared byrecrystallizing sublimation purified Aa*1 as a raw material once andfurther purifying it by sublimation again and then recrystallization.

1)-4 Crystallization Purification

Commercially available BPA was dissolved in a five-fold amount of phenolto obtain adduct crystals of bisphenol and phenol at 40° C. The phenolwas removed from the obtained adduct crystals by steam stripping at 5.33kPa (40 Torr) and 180° C. until the amount of phenol in BPA became 3%.Samples which had been purified by crystallization were designated asAc*1 and Ac*2 according to the number of times of crystallization.

2) Production of DPC

Raw Material 1 (Dg)

DPC is produced in accordance with a method described in “PlasticMaterial Lecture 17, Polycarbonate” written by Shoichi Sakajiri et al.,pp.45-46.

Raw Material 2

DPC is obtained by purifying DPC produced in accordance with Example 1of JP-A 7-188116 (Bayer AG) by a method described in “Plastic MaterialLecture 17, Polycarbonate” written by Shoichi Sakajiri et al., pp.45-46.

Raw Material 3

DPC is obtained by purifying DPC produced from commercially availabledimethyl carbonate in the presence of Ti(OBu)₄ as a catalyst inaccordance with Example 1 of JP-B 7-091230 (the term “JP-B” as usedherein means an “examined Japanese patent publication”) (Asahi ChemicalIndustry Co., Ltd.) by the above method.

The raw materials 2 and 3 had an extremely bad APHA (melt hazen colornumber) owing to impurities and were judged as difficult to be used.

3) Purification of DPC

3)-1 Sublimation Purification

The same apparatus as used for the sublimation purification of BPA wasused for DPC to carry out sublimation purification under a nitrogenatmosphere at a pressure of 30 Pa (0.3 Torr) and a temperature of 77° C.for 4 hours n number of times to obtain purified DPC.

A sample obtained by carrying out sublimation purification once wasdesignated as Da*1, a sample obtained by carrying out sublimationpurification twice was designated as Da*2, and samples obtained bycarrying out sublimation purification 3 times, 4 times and n number oftimes were designated as Da*3, Da*4, . . . , Da*n.

3)-2 Washing in Water+Distillation+Sublimation Purification

Separately from these, raw material DPC was washed in hot water (50° C.)three times, dried and distilled under vacuum in accordance with amethod described in “Plastic Material Lecture 17, Polycarbonate” writtenby Toshihisa Tatekawa (Nikkan Kogyo Shimbun Co., Ltd.), pp.45 to collecta fraction at 167 to 168° C. and 2,000 kPa (15 mmHg) which was furtherpurified by sublimation as described above to obtain purified diphenylcarbonate D-c.

3)-3 Ion Exchange Purification

The raw material DPC was dissolved in a ten-fold amount of acetone andlet pass through a cation and anion mixed ion exchange column, thesolvent was distilled off under vacuum, and the DPC was purified bysublimation to obtain purified diphenyl carbonate D-d.

Impurities contained in the purified bisphenol A and diphenyl carbonatewere measured by the above method and the results are shown in Tables 1to 3 below.

TABLE 1 non-metal impurities sample metal impurities (ppb by weight)(ppm by weight) name first elements second elements third ele- fourthelements of BPA purification Na Fe Cr Mn Ni Pb Cu Zn Pd In Al Si ment TiP N S Cl Br Ag raw material 86 60 5 4 8 5 1* 11 1* 7 22 25 1* 1* 1 1 301* Aa*1 one time of sublimation 20 42 3 2 1 1 1*  2 1* 4 13 14 1* 1* 1 112 1* purification A-Rme sublimation + one time of washing 20 42 3 2 1 11*  2 1* 4 13 14 1* 1* 1 1 12 1* A-Rac sublimation + one time of washing20 42 3 2 1 1 1*  2 1* 4 13 14 1* 1* 1 1 12 1* Aa*2 two times ofsublimation 10 26 1* 1* 1* 1* 1*  1* 1* 1*  1*  8 1* 1* 1* 1*  4 1*purification* Ac*1 one time of crystallization 45 35 2 1 1* 1* 1*  3 1*3 15 12 1* 1* 1* 1*  8 1* Ac*2 two times of crystallization 40 27 1 1 1*1* 1*  2 1* 1 11  7 1* 1* 1* 1*  2 1* Ab*1 one time of recrystallization19 43 2 4 2 1 1  2 1* 4 12 10 1* 1* 1* 1*  6 1* with acetone Ab*2 twotimes of recrystallization 17 22 1 2 1* 1* 1*  1 1* 2  8  5 1* 1* 1* 1* 2 1* with acetone Aab*2 two times of (sublimation +  5  8 1* 1* 1* 1*1*  1* 1* 1*  1*  3 1* 1* 1* 1*  1* 1* recrystallization with acetone)*1* indicates below detection limit.

TABLE 2 sample peak area ratio based on BPA name group A group B B:molecular weight: 307-309 of BPA purification (*10-3) (ppm) (ppm) Ag rawmaterial 3.2 86 55 Aa*1 one time of sublimation purification 2.7 66 36A-Rme sublimation + one time of washing 1.7 47 28 A-Rac sublimation +one time of washing 1.6 45 28 Aa*2 two times of sublimationpurification* 1.9 45 28 Ac*1 one time of crystallization 1.1 45 27 Ac*2two times of crystallization 1.6 11 17 Ab*1 one time ofrecrystallization 0.9 41 25 with acetone Ab*2 two times ofrecrystallization 0.8 11 5 with acetone Aab*2 two times of(sublimation + 0.6 10 4 recrystallization with acetone)* hazen sampleAPHA name organic impurities (ppm by weight) APHA retention of BPAnaphthol paraflavan codimer chromene xanthene 0 hour for 2 hours Ag 28071 63 21 32 30 60 Aa*1 230 65 50 18 22 20 40 A-Rme 166 29 27 11  8 10 25A-Rac 153 30 25  8  5 10 25 Aa*2 190 58 45 15 14 15 30 Ac*1 175 26 27  7 6 20 35 Ac*2 30  5*  5*  5*  5*  5 20 Ab*1 83 10 12  5*  5* 15 25 Ab*230  5*  5*  5*  5* 10 25 Aab*2 15  5*  5*  5*  5*  5 20 5* indicatesbelow detection limit.

TABLE 3 sample metal impurities (ppb by weight) name first elementssecond elements third element of DPC purification Na Fe Cr Mn Ni Pb CuZn Pd In Al Si Ti Dg raw material-1 96 40 15 5 5  1 1* 11 1* 15 42 15 1*Da*1 one time of sublimation 10 27  8 1 1  1 1  2 1*  4 21  7 1* D-cwashing in water, distillation + 10  9  1* 1* 1*  1* 1*  1* 1*  1*  1* 2 1* one time of sublimation* D-d acetone + ion exchange +  3  1*  1*1* 1*  1* 1*  1* 1*  1*  1*  1* 1* distillation raw material-2 25 45 167 7 10 1* 12 2  1* 12 11 1* raw material-3  3 25  8 2 2  1* 1*  3 1*  1* 6  6 2  hazen sample non-metal impurities (ppm by weight) APHA namefourth elements APHA retention of DPC P N S Cl Br 0 hour for 2 hours Dg1 2 1 2 1* 10 20 Da*1 1 1 1* 1 1* 5 15 D-c 1* 1* 1* 1 1* 5 15 D-d 1* 1*1* 1* 1* 5 15 2 5 1 2 3 10 40 1* 1 1* 1 1* 5 35 1* indicates belowdetection limit.

Comparative Example 1

An aromatic polycarbonate was produced as follows. 137 parts by weightof commercially available BPA (Ag) and 135 parts by weight of purifiedDPC (Da*1) as raw materials, and 8.2×10⁻⁶ part by weight of a disodiumsalt of bisphenol A and 5.5×10⁻³ part by weight of tetramethylammoniumhydroxide (to be abbreviated as TMAH hereinafter) as polymerizationcatalysts were charged into a reactor equipped with a stirrer,fractionating column and decompressor and molten at 180° C. under anitrogen atmosphere.

The inside pressure of the reactor was reduced to 13.33 kPa (100 mmHg)to carry out a reaction under agitation for 20 minutes while the formedphenol was distilled off. After the temperature was raised to 200° C.,the pressure was gradually reduced to carry out the reaction at 4,000kPa (30 mmHg) for 20 minutes while phenol was distilled off. Thereaction was further continued by gradually increasing the temperatureto 220° C. for 20 minutes, 240° C. for 20 minutes and 260° C. for 20minutes and then by reducing the pressure to 2.666 kPa (20 mmHg) at 260°C. for 10 minutes, 1.333 kPa (10 mmHg) for 5 minutes and finally at 260°C. and 66.7 Pa (0.5 mmHg) until the viscosity average molecular weightbecame 15,300.

Thereafter, 3.6×10⁻⁴ part by weight of tetrabutylphosphoniumdodecylbenzene sulfonate (to be abbreviated as DBSP) was added andstirred at 260° C. and 66.7 Pa (0.5 mmHg) for 10 minutes. The finallyobtained aromatic polycarbonate had a viscosity average molecular weightof 15,300, a terminal hydroxyl group concentration of 86, a phenoxyterminal group concentration of 154 eq/ton-polycarbonate) and a meltviscosity stability of 0.

Comparative Example 2

Polymerization was carried out in the same manner as in ComparativeExample 1 except that 1.7×10⁻² part by weight of tetrabutylphosphoniumhydroxide (to be abbreviated as TBPH hereinafter) was used in place ofTMAH. The finally obtained aromatic polycarbonate had a viscosityaverage molecular weight of 15,300, a terminal hydroxyl groupconcentration of 87, a phenoxy terminal group concentration of 152(eq/ton-polycarbonate) and a melt viscosity stability of 0.

Example 1

The aromatic polycarbonate obtained in Comparative Example 1 wasdissolved in 1.5×10³ parts by weight of NMP for the electronic industry,1.1×10⁻⁴ parts by weight of methanol for the electronic industry wasadded to separate the precipitated polymer by filtration, and thepolymer was dried at 13.3 Pa (0.1 mmHg) and 100° C. for 24 hours. Theobtained aromatic polycarbonate had a viscosity average molecular weightof 15,300, a terminal hydroxyl group concentration of 85, a phenoxyterminal group concentration of 154 (eq/ton-polycarbonate) and a meltviscosity stability of 0.

Example 2

2-methoxycarbonylphenylphenyl carbonate (to be abbreviated as SAMhereinafter) was added in an amount of 8.0×10⁻³ part by weight based on1 part by weight of a polymer when the viscosity average molecularweight of a polycarbonate became 15,300 in the production of thepolycarbonate in Comparative Example 1 and stirred at 260° C. and 133.3Pa (1 mmHg) for 10 minutes. Thereafter, 2.3×10⁻⁶ part by weight of DBSPwas added and stirred at 260° C. and 66.7 Pa (0.5 mmHg) for 10 minutes.

The obtained aromatic polycarbonate was dissolved in 1.5×10³ parts byweight of NMP for the electronic industry, 1.1×10⁴ parts by weight ofmethanol for the electronic industry was added to separate theprecipitated polymer by filtration, and the polymer was dried at 13.3 Pa(0.1 mmHg) and 100° C. for 24 hours. The obtained aromatic polycarbonatehad a viscosity average molecular weight of 15,300, a terminal hydroxylgroup concentration of 60, a phenoxy terminal group concentration of 179(eq/ton-polycarbonate) and a melt viscosity stability of 0.

Example 3

The procedure of Example 2 was repeated except that SAM was used in anamount of 17.6×10⁻³ part by weight based on 1 part by weight of thepolymer. The obtained aromatic polycarbonate had a viscosity averagemolecular weight of 15,300, a terminal hydroxyl group concentration of30, a phenoxy terminal group concentration of 209 (eq/ton-polycarbonate)and a melt viscosity stability of 0.

Example 4

Melt polymerization was carried out in the same manner as in ComparativeExample 1 except that purified BPA (Ac*1) and purified DPC (Da*1) wereused. After polymerization, SAM and DBSP were used in the same manner asin Example 3. The finally obtained aromatic polycarbonate had aviscosity average molecular weight of 15,300, a terminal hydroxyl groupconcentration of 30, a phenoxy terminal group concentration of 209(eq/ton-polycarbonate) and a melt viscosity stability of 0.

Example 5

The aromatic polycarbonate obtained in Comparative Example 1 wasdissolved in 1.5×10³ parts by weight of NMP for the electronic industryand treated with activated carbon, and 1.1×10⁴ parts by weight ofmethanol for the electronic industry was added dropwise under agitationat a rate of 1×10² parts by weight/min to separate the precipitatedpolymer by filtration. This reprecipitation operation was repeated twiceand the obtained polymer was dried at 13.3 Pa (0.1 mmHg) and 100° C. for24 hours. The obtained polycarbonate had a viscosity average molecularweight of 15,300, a terminal hydroxyl group concentration of 85, aphenoxy terminal group concentration of 154 (eq/ton-polycarbonate) and amelt viscosity stability of 0.

Example 6

Melt polymerization was carried out in the same manner as in ComparativeExample 1 except that purified BPA (Ab*2) and purified DPC (D-c) wereused. After polymerization, SAM and DBSP were used as in Example 3. Thefinally obtained aromatic polycarbonate had a viscosity averagemolecular weight of 15,300, a terminal hydroxyl group concentration of30, a phenoxy terminal group concentration of 209 (eq/ton-polycarbonate)and a melt viscosity stability of 0.

Example 7

The procedure of Example 6 was repeated except that TMAH was used in anamount of 5.5×10⁻² part by weight. The finally obtained aromaticpolycarbonate had a viscosity average molecular weight of 15,300, aterminal hydroxyl group concentration of 30, a phenoxy terminal groupconcentration of 209 (eq/ton-polycarbonate) and a melt viscositystability of 0.

Example 8

The aromatic polycarbonate obtained in Comparative Example 1 wasdissolved in 1.5×103 parts by weight of NMP for the electronic industryand treated with a mixed ion exchange resin column, and 1.1×10⁴ parts byweight of methanol for the electronic industry was added dropwise underagitation at a rate of 1×10² parts by weight/min to separate theprecipitated polymer by filtration. This reprecipitation operation wasrepeated twice and the obtained polymer was dried at 13.3 Pa (0.1 mmHg)and 100° C. for 24 hours. The finally obtained aromatic polycarbonatehad aviscosity average molecular weight of 15,300, a terminal hydroxylgroup concentration of 85, a phenoxy terminal group concentration of 154(eq/ton-polycarbonate) and a melt viscosity stability of 0.

Example 9

Melt polymerization was carried out in the same manner as in ComparativeExample 1 except that purified BPA (Aab*2) and purified DPC (D-d) wereused. After polymerization, SAM and DBSP were used as in Example 3. Thefinally obtained aromatic polycarbonate had a viscosity averagemolecular weight of 15,300, a terminal hydroxyl group concentration of30, a phenoxy terminal group concentration of 209(eq./ton-polycarbonate) and a melt viscosity stability of 0.

Comparative Example 3

Raw materials, and 8.2×10⁻⁵ part by weight of a disodium salt ofbisphenol A and 5.5×10⁻³ part by weight of TMAH as polymerizationcatalysts were charged into a reactor equipped with a stirrer,fractionating column and decompressor and molten at 180° C. under anitrogen atmosphere as in Comparative Example 1.

The inside pressure of the reactor was reduced to 13.33 kPa (100 mmHg)to carry out a reaction under agitation for 20 minutes while the formedphenol was distilled off. After the temperature was raised to 200° C.,the pressure was gradually reduced to carry out the reaction at 4.000kPa (30 mmHg) for 20 minutes while phenol was distilled off. Thereaction was further continued by gradually increasing the temperatureto 220° C. for 20 minutes, 240° C. for 20 minutes and 260° C. for 20minutes and then by reducing the pressure to 2.666 kPa (20 mmHg) at 260°C. for 10 minutes, 1.333 kPa (10 mmHg) for 5 minutes and finally at 280°C. and 66.7 Pa (0.5 mmHg) until the viscosity average molecular weightbecame 15,300.

Thereafter, 1.3×10⁻³ part by weight of DBSP was added and stirred at280° C. and 66.7 Pa (0.5 mmHg) for 10 minutes to obtain an aromaticpolycarbonate. The obtained aromatic polycarbonate had a viscosityaverage molecular weight of 15,300, a terminal hydroxyl groupconcentration of 85, a phenoxy terminal group concentration of 154eq/ton-polycarbonate and a melt viscosity stability of 0.

Comparative Example 4

(Mw=22,500)

The polymerization of the aromatic polycarbonate was further continuedin Comparative Example 1 to obtain a polycarbonate having a viscosityaverage molecular weight of 22,500 in the end. The obtained aromaticpolycarbonate had aviscosity average molecular weight of 22,500, aterminal hydroxyl group concentration of 73, a phenoxy terminal groupconcentration of 77 eq/ton-polycarbonate and a melt viscosity stabilityof 0.

Examples 10 and 11

The aromatic polycarbonate obtained in Comparative Example 4 was treatedin the same manner as in Example 1 and Example 8. The obtainedpolycarbonates had a viscosity average molecular weight of 22,500, aterminal hydroxyl group concentration of 73, a phenoxy terminal groupconcentration of 77 eq/ton-polycarbonate and a melt viscosity stabilityof 0.

Comparative Example 5

502.8 g (2.21 mols) of raw material bisphenol A, 2.21 liters (4.19 molsof sodium hydroxide) of a 7.2% sodium hydroxide aqueous solution and0.98 g (0.0056 mol) of hydrosulfite sodium were charged into a 5-literreactor equipped with a phosgene blowing tube, thermometer and stirrerand dissolved, 1.27 liters of methylene chloride and 80.70 g (0.98 molof sodium hydroxide) of a 48.5% sodium hydroxide aqueous solution wereadded under agitation, and 250.80 g (0.253 mol) of phosgene was added at25° C. over 180 minutes to carry out a phosgenation reaction.

After the end of the phosgenation reaction, 17.51 g (0.117 mol) ofp-tert-butylphenol, 80.40 g (0.97 mol) of a 48.5% sodium hydroxideaqueous solution and 1.81 ml (0.013 mol) of triethylamine as a catalystwere added, maintained at 33° C. and stirred for 2 hours to complete thereaction. A methylene chloride layer was separated from the reactionmixed solution which was then purified by washing in water times toobtain a polycarbonate resin having a viscosity average molecular weightof 15,300, a terminal hydroxyl group concentration of 15, a terminalphenoxy group concentration of 224 eq./ton-polycarbonate and a meltviscosity stability of 0.1.

Example 12

The same treatment as in Example 1 was made on the polymer ofComparative Example 5. Finally, a polycarbonate resin having a viscosityaverage molecular weight of 15,300, a terminal hydroxyl groupconcentration of 15, a terminal phenoxy group concentration of 224eq./ton-polycarbonate and a melt viscosity stability of 0 was obtained.The contents of impurities (unit: ppm, ppb) in thearomaticpolycarbonates obtained in Examples 1 to 12 and ComparativeExamples 1 to 5 are shown in Table 4 below.

TABLE 4 metal impurities (ppb by weight) non-metal impurities (ppm thirdby weight) Experiment terminal first elements second elements elementfourth elements No. BPA DPC OH Na Fe Cr Mn Ni Pb Cu Zn Pd In Si Al Ti PN S Cl Br C.Ex. 1 Ag Da*1 85 95 79 10 4 8 6 7  9 1* 11 21 16 1* 1* 2 2 41* C.Ex. 2 Ag Da*1 87 78 89 12 6 8 7 6  7 1* 10 30 21 1* 3 1* 2 8 1* Ex.1 Ag Da*1 85 62 55  5 2 1 2 3  5 1*  3 17 11 1* 1* 2 1 3 1* Ex. 2 AgDa*1 60 61 57  4 2 1 2 3  6 1*  3 16 11 1* 1* 2 1 3 1* Ex. 3 Ag Da*1 3062 56  5 2 1 2 4  5 1*  4 15 10 1* 1* 2 1 3 1* Ex. 4 Ac*1 Da*1 30 58 54 9 2 1* 1* 1*  4 1*  6 28 17 1* 1* 1 1* 1* 1* Ex. 5 Ag Da*1 85 29 35  11* 1* 1* 1  1 1*  1  3  2 1* 1* 1* 2 2 1* Ex. 6 Ab*2 D-c 30 32 25  1 21* 1* 1*  1* 1*  1*  4  6 1* 1* 1 1* 1* 1* Ex. 7 Ab*2 D-c 30 32 25  1 21* 1* 1*  1* 1*  1*  4  6 1* 1* 2 1* 1* 1* Ex. 8 Ag Da*1 85 18 16  1 1*1* 1* 1*  1* 1*  1*  1  1 1* 1* 1* 1* 1* 1* Ex. 9 Aab*2 D-d 30 16 7  1*1* 1* 1* 1*  1* 1*  1*  4  1* 1* 1* 1 1* 1* 1* C.Ex. 3 Ag Da*1 85 175 8212 1 2 1 1  5 1*  3 21 18 1* 1* 2 2 4 1* C.Ex. 4 Ag Da*1 73 95 80 10 4 77 6  8 1* 10 23 18 1* 1* 1 2 3 1* Ex. 10 Ag Da*1 73 66 56  7 3 1 2 4  51*  5 16 12 1* 1* 2 1 2 1* Ex. 11 Ag Da*1 73 18 17  4 1* 1* 1* 1*  1* 1* 1*  1  1 1* 1* 1* 1* 1* 1* C.Ex. 5 Ag Da*1 15 25 81  1 2 2 2 8 10 1*  621 18 1* 1* 1* 1* 7 1* Ex. 12 Ag Da*1 15 12 60  6 1* 1* 1* 4  4 1*  6 1613 1* 1* 1* 1* 1 1* Ex.: Example C.Ex.: Comparative Example 1* indicatesbelow detection limit.

The physical properties of the aromatic polycarbonates obtained inExamples 1 to 12 and Comparative Examples 1 to are shown in Table 5below.

TABLE 5 initial physical properties OH physical properties afterdurability test concentration color deterioration impact strengthtransparency polymerization eg/ton- L b in color retention retentionExample degree polycarbonate value value Δb value (%) (%) C.Ex. 1 15,30085 65 0.9 2 87 88 C.Ex. 2 15,300 85 64 1.1 2.1 88 88 Ex. 1 15,300 85 650.9 0.9 93 91 Ex. 2 15,300 60 65 0.9 0.8 93 92 Ex. 3 15,300 30 65 0.90.7 93 93 Ex. 4 15,300 30 65 0.8 0.7 93 93 Ex. 5 15,300 85 65 0.7 0.7 9394 Ex. 6 15,300 30 65 0.7 0.6 93 94 Ex. 7 15,300 30 65 0.8 0.7 92 93 Ex.8 15,300 85 65 0.7 0.6 93 95 Ex. 9 15,300 30 65 0.7 0.6 93 95 C.Ex. 315,300 85 64 0.9 2.5 85 86 C.Ex. 4 22,500 73 63 1.3 1.4 94 89 Ex. 1022,500 73 63 1.2 0.9 97 92 Ex. 11 22,500 73 64 1.2 0.7 97 93 C.Ex. 515,300 15 67 0.8 1.7 89 89 Ex. 12 15,300 15 67 0.7 0.7 90 92 Ex.:Example C.Ex.: Comparative Example

Examples 13 and 14 and Comparative Example 6

0.01 wt % of tris(2,4-di-t-butylphenyl)phosphite and 0.08 wt % ofglycerol monostearate were added to each of the aromatic polycarbonatesof Examples 8 and 9 and Comparative Example 3. The obtained compositionwas molten and kneaded by a vented double-screw extruder (KTX-46 of KobeSteel, Ltd.) at a cylinder temperature of 240° C. while it was degassedto obtain pellets. The pellets were used to carry out a temperature andhumidity deterioration test for DVD (DVD-Video) disk substrates.

A melt mold special for DVDs was attached to the DISK3 M III injectionmolding machine of Sumitomo Heavy Industries, Ltd., a nickel DVD stamperhaving information including an address signal was set in this metalmold, the above pellets were injected into the hopper of a moldingmachine automatically, and a DVD disk substrate having a diameter of 120mm and a thickness of 0.6 mm was molded at a cylinder temperature of380° C., a metal mold temperature of 115° C., an injection speed of 200mm/sec and a retention pressure of 3,432 kPa (35 kgf/cm²).

To test the long-term reliability of an optical disk under severetemperature and humidity conditions, the aromatic polycarbonate opticaldisk substrate was maintained at a temperature of 80° C. and a relativehumidity of 85% for 1,000 hours and then evaluated by the followingmeasurement. Number of formed white points: The optical disk substrateafter the temperature and humidity deterioration test was observedthrough a polarization microscope to count the number of formed whitepoints of 20 μm or more in size. This was made on 25 optical disksubstrates (diameter of 120 mm) to obtain a mean value which was takenas the number of white points.

As a result, the numbers of white points of Examples 13 and 14 andComparative Example 6 were 0.2, 0.1 and 3.5, respectively.

Example 15

After the aromatic polycarbonate of Example 10 was molten, it wassupplied to the T die of a molding machine by a gear pumpquantitatively. 0.003 wt % of trisnonylphenyl phosphate was added beforethe gear pump and the aromatic polycarbonate was melt extruded into theform of a sheet having a thickness of 2 mm or 0.2 mm and a width of 800mm while it was sandwiched between a mirror surface cooling roll and amirror surface roll or contacted on one side.

A visible light curable plastic adhesive (BENEFIX PC of Ardel Co., Ltd.)was applied to one side of the obtained aromatic polycarbonate sheet(thickness of 2 mm) to form an adhesive layer on the sheet while thesheet was extruded in one direction such that air bubbles were notcontained in the sheet and exposed to light having an energy of 5,000mJ/cm² by an optical curing device equipped with a visiblelight-exclusive metal halide lamp to obtain a laminate. When theadhesive strength of the obtained laminate was measured in accordancewith JIS K-6852 (compression shear adhesive strength test method), itwas 10.4 MPa (106 Kgf/cm²).

A uniform mixed solution of ink (Natsuda 70-9132: color 136D smoke) anda solvent (isophorone/cyclohexane/isobutanol=40/40/20 (wt %)) wasprinted on a 0.2 mm thick aromatic polycarbonate sheet by a silk screenprinter and dried at 100° C. for 60 minutes. The ink printed surface wassatisfactory without a transfer failure.

Separately, a sheet (thickness of 0.2 mm) printed with printing inkprepared by mixing 30 parts of a polycarbonate resin (specific viscosityof 0.895, Tg of 175° C.) obtained from general interfacialpolycondensation between 1,1-bis(4-hydroxyphenyl)cyclohexane andphosgene, 15 parts of Plast Red 8370 (of Arimoto Kagaku Kogyo Co., Ltd.)as a dye and 130 parts of dioxane as a solvent was placed in aninjection molding metal mold and polycarbonate resin pellets (PanliteL-1225 of Teijin Chemicals, Ltd.) were insert molded at 310° C. Thepattern of the printed portion of the molded product after insertmolding had no abnormalities such as blotches and blurry spots and aninsert molded product whose printed portion had a good appearance wasobtained.

Examples 16 to 22

0.003 wt % of trisnonylphenyl phosphite and 0.05 wt % of trimethylphosphate were added to the aromatic polycarbonate of Example 10 anduniformly mixed to obtain aromatic polycarbonate powders. The powdersand components (shown by the following symbols) in Tables 6 and 7 wereuniformly mixed together using a tumbler, the resulting mixture waspelletized by a 30 mm-diameter vented double-screw extruder (KTX-30 ofKobe Steel, Ltd.) at a cylinder temperature of 260° C. and a vacuumdegree of 1.33 kPa (10 mmHg) while it was degassed, and the obtainedpellets were dried at 120° C. for 5 hours and molded into a measurementpiece by an injection molding machine (SG150U of Sumitomo HeavyIndustries, Ltd.) at a cylinder temperature of 270° C. and a metal moldtemperature of 80° C. to carry out the following evaluations. Theresults are shown in Tables 6 and 7.

(1)-1 ABS: styrene-butadiene-acrylonitrile copolymer; Suntac UT-61;Mitsui Chemicals, Inc.

(1)-2 AS: styrene-acrylonitrile copolymer; Stylax-AS 767 R27; AsahiChemical Industry, Co., Ltd.

(1)-3 PET: polyethylene terephthalate; TR-8580; Teijin Limited,intrinsic viscosity of 0.8

(1)-4 PBT: polybutylene terephthalate; TRB-H; Teijin Limited, intrinsicviscosity of 1.07

(2)-1 MBS: methyl (meth)acrylate-butadiene-styrene copolymer; KaneaceB-56; Kaneka Corporation

(2)-2 E-1: butadiene-alkyl acrylate-alkyl methacrylate copolymer;Paraloid EXL-2602; Kureha Chemical Industry, Co., Ltd.

(2)-3 E-2: composite rubber comprising a polyorganosiloxane componentand a polyalkyl(meth)acrylate rubber component which form aninterpenetrating network structure; Metabrene S-2001; Mitsubishi RayonCo., Ltd.

(3)-1 T: talc; HS-T0.8; Hayashi Kasei Co., Ltd., average particlediameter L measured by laser diffraction method=5 μm, L/D=8

(3)-2 G: glass fiber; chopped strand ECS-03T-511; Nippon Electric GlassCo., Ltd., urethane focusing treatment, fiber diameter of 13 μm

(3)-3 W: wollastonite; Sikatec NN-4; Tomoe Kogyo Co., Ltd., numberaverage fiber diameter D obtained by observing through an electronmicroscope =1.5 μm, average fiber length=17 μm, aspect ratio L/D=20

(4) WAX: olefin-based wax obtained by copolymerizing α-olefin and maleicanhydride; Diacalna-P30; Mitsubishi Kasei Corporation (content of maleicanhydride=10 wt %)

(A) Flexural Modulus

This was measured in accordance with ASTM D790.

(B) Notched Impact Value

This was measured by striking a weight against a 3.2 mm thick test piecefrom the notch side in accordance with ASTM D256.

(C) Fluidity

This was measured by an Archimedes type spiral flow (thickness of 2 mm,width of 8 mm) at a cylinder temperature of 250° C., a metal moldtemperature of 80° C. and an injection pressure of 98.1 MPa.

(D) Chemical Resistance

A 1% distortion was added to a tensile test piece used in ASTM D638 andimmersed in 30° C. Esso regular gasoline for 3 minutes and then thetensile strength of the test piece was measured to calculate retention.The retention was calculated from the following expression.

retention (%)=(strength of treated sample/strength of untreatedsample)×100

TABLE 6 Ex. 16 Ex. 17 Ex. 18 Ex. 19 com- polycarbonate wt % 60 60 60 60position of Example 10 ABS wt % 40 40 40 — AS wt % — — — 30 MBS wt % — —— 10 total wt parts 100 100 100 100 G wt parts 15 — — 15 W wt parts — 15— — T wt parts — — 15 — WAX wt parts — 1 1 — charac- flexural MPa 3,4503,200 2,900 3,300 teristic modulus proper- fluidity cm 30 27 29 34 tiesnotched impact J/m 75 70 50 85 value Ex.: Example

TABLE 7 Ex. 20 Ex. 21 Ex. 28 composition polycarbonate of wt % 70 70 70Example 10 PBT wt % — 30 5 PET wt % 30 — 25 total wt parts 100 100 100E-1 wt parts 5 5 — E-2 wt parts — — 5 G wt parts 20 — — W wt parts — 10— T wt parts — — 10 WAX wt parts — 1 1 characteristic flexural modulusMPa 5,770 3,560 3,400 properties modulus chemical resistance % 89 85 83notched impact J/m 215 540 519 value

Effect of the Invention

The durability, especially long-term durability under severe temperatureand humidity conditions of a polymer is greatly improved and theexcellent color, transparency and mechanical strength of the polymer areretained by suppressing the contents of specific impurities in thearomatic polycarbonate to specific values or less as in the presentinvention.

An aromatic polycarbonate resin having excellent stability can beproduced by polymerizing DPC and BPA whose contents of specific metalelements are specific values or less as raw materials.

What is claimed is:
 1. An aromatic polycarbonate which comprises a mainrecurring unit represented by the following formula (1):

wherein R₁ and R₂ are each independently alkyl group having 1 to 20carbon atoms, alkoxy group having 1 to 20 carbon atoms, cycloalkyl grouphaving 6 to 20 carbon atoms, aryl group having 6 to 20 carbon atoms,cycloalkoxy group having 6 to 20 carbon atoms or aryloxy group having 6to 20 carbon atoms, m and n are each independently an integer of 0 to 4,and X is a single bond, oxygen atom, carbonyl group, alkylene grouphaving 1 to 20 carbon atoms, alkylidene group having 2 to 20 carbonatoms, cycloalkylene group having 6 to 20 carbon atoms, cycloalkylidenegroup having 6 to 20 carbon atoms, arylene group having 6 to 20 carbonatoms or alkylene-arylene-alkylene group having 6 to 20 carbon atoms,and terminal groups consisting essentially of aryloxy groups (A) andphenolic hydroxyl groups (B), the (A)/(B) molar ratio being 95/5 to40/60, and which has a melt viscosity stability measured under anitrogen stream at a shear rate of 1 rad./sec and 300° C. for 30 minutesof 0.5% or less, a sodium metal element content of 100 ppb or less and acontent of each of first elements, Ni, Pb, Cr, Mn and Fe of 70 ppb orless, and wherein the relationship between the concentration (H)(eq./ton-polycarbonate) of terminal hydroxyl groups and the totalcontent (Σfirst elements) (ppb) of the first elements is represented by(H)≦Σfirst elements.
 2. The aromatic polycarbonate of claim 1, whereinthe content of each of the first elements is 40 ppb or less.
 3. Thearomatic polycarbonate of claim 1, wherein the content of sodium metalelement is 70 ppb or less and the content of each of the first elementsis 20 ppb or less.
 4. The aromatic polycarbonate of claim 1, wherein thecontent of sodium metal element is 20 ppb or less and the content ofeach of the first elements is 10 ppb or less.
 5. The aromaticpolycarbonate of claim 1, wherein the relationship between theconcentration (H) (eq./ton-polycarbonate) of terminal hydroxyl groupsand the total content (Σfirst elements) (ppb) of the first elements isrepresented by (H)≦0.5×(Σfirst elements).
 6. The aromatic polycarbonateof claim 1, wherein the content of each of second elements Cu, Zn, Pd,In, Si and Al, is 20 ppb or less.
 7. The aromatic polycarbonate of claim1, wherein the content of a third element Ti is 1 ppb or less and thecontent of each of fourth elements P, N, S, Cl and Br is 1 ppm or less.8. A molded product of the aromatic polycarbonate of any one of claim 1,6 or
 7. 9. The molded product of claim 8 which is an optical disksubstrate.
 10. A method for producing a polycarbonate which comprisespolycondensing an aromatic dihydroxy compound and a carbonic aciddiester in the presence of a catalyst containing a) at least one basiccompound selected from the group consisting of a nitrogen-containingbasic compound and a phosphorus-containing basic compound in an amountof 10 to 1,000μ chemical equivalents based on 1 mol of the aromaticdihydroxy compound and b) at least one compound selected from the groupconsisting of an alkali metal compound and an alkali earth metalcompound in an amount of 0.05 to 5μ chemical equivalents based on 1 molof the aromatic dihydroxy compound, wherein the aromatic dihydroxycompound and the carbonic acid diester having 1) a sodium metal elementcontent of 52 ppb or less and 2) a content of each of first elements Fe,Cr, Mn, Ni and Pb of 40 ppb or less are used, and 3) the amount of thebasic compound based on 1 mol of the aromatic dihydroxy compound is notmore than 20×(Fe*)+200 based on the total weight Fe* (ppb) of Fecontained in the aromatic dihydroxy compound and Fe contained in thecarbonic acid diester.
 11. The method of claim 10, wherein the aromaticdihydroxy compound and the carbonic acid diester each have 1) a sodiummetal element content of 35 ppb or less by weight and 2) a content ofeach of the first elements of 23 ppb or less by weight.
 12. The methodof claim 10, wherein the aromatic dihydroxy compound and the carbonicacid diester each have 1) a sodium metal element content of 6 ppb orless by weight and 2) a content of each of the first elements of 6 ppbor less by weight.
 13. The method of claim 10, wherein the aromaticdihydroxy compound and the carbonic acid diester each have a content ofeach of second elements Cu, Zn, In, Pd, Si and Al of 10 ppb or less byweight.
 14. The method of claim 10, wherein the aromatic dihydroxycompound and the carbonic acid diester each have a content of a thirdelement Ti of 1 ppb or less by weight and a content of each of fourthelements P, N, S, Cl and Br of 1 ppm or less by weight.
 15. The methodof claim 10, wherein the aromatic dihydroxy compound is bisphenol A. 16.The method of claim 15, wherein when the bisphenol A is analyzed byhigh-speed liquid chromatography (using a 0.1% phosphoric acid aqueoussolution as an elute A and acetonitrile as an elute B, this measurementis carried out at a total flow rate of the elute A and the elute B of0.9 ml/min when the elute A/elute B ratio is 1:1 for 5 minutes after thestart of measurement with a high-speed liquid chromatograph comprising acolumn having an inner diameter of 4.6 mm and a length of 250 mm, filledwith an adsorbent prepared by bonding 15% (amount of carbon) of anoctadecyl group to a high-purity spherical silica gel having a porediameter of 100 Å and maintained at 40° C.±0.1° C., and then gradientoperation is carried out by continuously increasing the amount of theelute B after 5 minutes from the start of measurement so that the ratioof the elute A to the elute B becomes 0:1 in 55 minutes after the startof measurement while the total flow rate is fixed, to analyze BPA with adetector for ultraviolet light having a wavelength of 254 nm), the ratioof the total of the absorption peak areas of compounds eluting for 15.5to 24 minutes to the absorption peak area of bisphenol A is 2.0×10⁻³ orless.
 17. The method of claim 16, wherein the ratio of the total of theabsorption peak areas of the eluting compounds to the absorption peakarea of bisphenol A is 1.0×10⁻³ or less.
 18. The method of claim 16,wherein when bisphenol A is analyzed by high-speed liquidchromatography, the ratio of the total of the absorption peak areas ofcompounds eluting for 22 to 24 minutes to the absorption peak area ofbisphenol A is 5×10⁻⁵ or less.
 19. The method of claim 18, wherein whenbisphenol A is analyzed by high-speed liquid chromatography, the ratioof the total of the absorption peak areas of compounds eluting for 22 to24 minutes and having a molecular weight of 307 or more and 309 or lessto the absorption peak area of bisphenol A is 2×10⁻⁵ or less.
 20. Themethod of claim 16, wherein bisphenol A has a total content of1-naphthols represented by the following formula (2):

wherein R₃ and R₄ are each independently methyl, ethyl, n-propyl,isopropyl or isopropenyl, of 2×10⁻⁴ part or less by weight based on 1part by weight of bisphenol A.
 21. The method of claim 20, wherein thetotal content of 1-napthols is 1×10⁻⁴ part or less by weight based on 1part by weight of bisphenol A.
 22. The method of claim 16, whereinbisphenol A contains a paraflavan compound represented by the followingformula (3):

wherein R₅ to R₇ are each independently an alkyl group having 1 to 4carbon atoms, R₈ and R₉ are each independently an alkyl group having 1to 4 carbon atoms, and p and q are each independently an integer of 0 to4, in an amount of 5×10⁻⁵ part or less by weight based on 1 part byweight of bisphenol A, and a codimer derivative represented by thefollowing general formula (4):

wherein R₁₀ to R₁₂ are each independently an alkyl group having 1 to 4carbon atoms, R₁₃ and R₁₄ are each independently an alkyl group having 1to 4 carbon atoms, and s and t are each independently an integer of 0 to4, in an amount of 5×10⁻⁵ part or less by weight based on 1 part byweight of bisphenol A.
 23. The method of claim 16, wherein bisphenol Acontains a chromene compound represented by the following formula (5):

wherein R₁₅ to R₁₇ are each independently an alkyl group having 1 to 4carbon atoms, R₁₈ is a hydrogen atom or alkyl group having 1 to 4 carbonatoms, and a is an integer of 0 to 4, in an amount of 1×10⁻⁵ part orless by weight based on 1 part by weight of bisphenol A, and a compoundrepresented by the following formula (6):

wherein R₁₉ and R₂₀ are each independently an alkyl group having 1 to 4carbon atoms, R₂₁ and R₂₂ are each independently an alkyl group having 1to 4 carbon atoms, and b and c are each independently an integer of 0 to4, in an amount of 1×10⁻⁵ part or less by weight based on 1 part byweight of bisphenol A.